1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, one, three or four horizontal and vertical neighbors.

A211049

1/3 the number of n X n 0..2 symmetric matrices with every element equal to zero, one, three or four horizontal and vertical neighbors.

Terms

    a(0) =1a(1) =4a(2) =48a(3) =1232a(4) =69944a(5) =8897744a(6) =2543744944

External references